On Thursday, 28 November 2013 at 19:22:06 UTC, Andrei
Alexandrescu wrote:
Interesting. Could you please create a paste with the two code
samples?
Thanks,
Andrei
Hello,
here is the Go code:
package main
import (
"fmt"
)
type Point struct {
x, y int
}
type Rectangular struct {
topLeft, bottomRight Point
}
func (self Rectangular) Left() int {
return self.topLeft.x
}
func (self Rectangular) Right() int {
return self.bottomRight.x
}
func (self Rectangular) Width() int {
return self.Right() - self.Left()
}
type Rectangle struct {
Rectangular
}
func NewRectangle(topLeft, bottomRight Point) *Rectangle {
rectangle := new(Rectangle)
rectangle.Rectangular.topLeft = topLeft
rectangle.Rectangular.bottomRight = bottomRight
return rectangle
}
func main() {
rectangle := NewRectangle(Point{1, 2}, Point{12, 2})
fmt.Println(rectangle.Width())
}
And this is the Scala code:
import java.awt.Point
trait Rectangular {
protected val topLeft: Point
protected val bottomRight: Point
def width : Int = bottomRight.x - topLeft.x
}
class Rectangle(val topLeft: Point, val bottomRight: Point)
extends Rectangular
object RunIt extends Application {
val rectangle = new Rectangle(new Point(1, 2), new Point(12, 2))
println(rectangle.width)
}
I guess in D you would do something like this:
mixin template Rectangular() {
Point x, y;
}
mixin Rectangular;
struct Rectangle {
mixin Rectangular;
}
Note that in the Scala code Rectangular.topLeft and
Rectangular.bottomRight are protected. Since the solution in Go
makes use of delegation this can only be accomplished in Go
through making getters public or defining Rectangle in the same
package as Rectangular. Since Go does not have constructors the
way to initialize a Rectangle in Go looks more clumsy.
An interesting point to me is that Rectangular in Go is just an
ordinary struct whereas Rectangular is a special construct in
Scala (being a trait) and in D (being a mixin). So Scala and D
force you to design ahead, e.g. you have to decide in advance
whether to make Rectangular a trait or mixin. Thereafter,
Rectangular is not of use on its own, only when used as a trait
or mixin.
What makes me think is whether delegation as a language construct
has been underrated and whether Go now makes this obvious.
-- Bienlein
